An intriguing new study from the University of Oxford has explored how bird songs evolve over time.
Researchers spent three years collecting over 20,000 hours of sound recordings from a wild population of great tits (Parus major) in Wytham Woods, Oxfordshire, which has been studied for the past 77 years as part of the Wytham Great Tit Study.
Artificial Intelligence (AI) was used to identify individual birds based on their solo songs and to measure song differences between individuals, in order to track how the local ‘music scene’ or collective bird song in a wild population changes over time.
Just as human communities develop distinct dialects and musical traditions, some birds also evolve local song cultures. The goal of the study was to investigate how the movement, age and turnover of birds within a population influences the diversity and evolution of their songs, including which songs become locally popular, which songs fade away, and how varied their song repertoires become.
“We wanted to see if the same processes that shape bird populations in a traditional evolutionary sense also influence their songs, since great tits learn their songs, rather than inheriting them genetically,” says lead researcher Dr Nilo Merino Recalde from the Department of Biology at the University of Oxford.
“Our study provides real-world evidence that demographic factors, such as age, movement patterns, and population turnover, play a key role in shaping the songs we hear in bird populations. We were excited to find clear evidence that even at small scales (within neighbourhoods, rather than whole populations), the movements and life histories of individual birds actively shape the songs they sing.”
The study found that birds of similar age tend to have more similar repertoires, with mixed-age neighbourhoods having a higher ‘cultural diversity’.
Older birds can function as ‘cultural repositories’ of older song types that younger birds may not know, just as human grandparents might remember songs teenagers have never heard.
But age isn’t the only factor influencing song evolution. The study also found that when birds mix more, through increased local dispersal and the arrival of immigrants, they tend to adopt more common songs. Areas where birds stay close to their birthplace maintain more diverse and unique ‘homegrown’ song cultures, similar to how isolated human communities often develop distinct dialects or musical styles.
The pace of song turnover within neighbourhoods is driven by individuals coming and going. When birds leave or die, many song types disappear with them. Young birds that replace departed and ‘dearly departed’ birds can speed up the adoption of new types of songs.
The results also indicated that newcomers to a population tend to adopt local songs, rather than introducing entirely new tunes. But they also tend to learn more songs overall, enriching the local ‘music scene’.
The findings, based on an analysis of over 100,000 bird songs, were published today in the journal Current Biology.
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Are there practical applications to this kind of research? “Studying how birdsong changes over time helps us understand how learned traits evolve and how demographic factors shape this process,” explains Recalde.
“We believe changes in birdsong can signal shifts in population structure, health, or environmental conditions. For that reason, acoustic monitoring is emerging as a non-invasive and effective way to track these changes and monitor populations, providing valuable insights for conservation efforts.”
Human-caused factors, such as climate change and habitat loss, are changing the make-up of bird populations, which will in turn impact bird song. “Since many species learn their songs from others, changes in the number and identity of ‘tutors’ can impact how songs evolve over time and the level of diversity that can be maintained,” Recalde says. “Factors like anthropogenic noise can also drive shifts in songs. Also, habitat loss and the decline of subpopulations can lead to a loss of both genetic and cultural diversity, including unique song types that have developed over generations and that may, sadly, disappear.”
The well-known population of great tits in Wytham Woods provided extensive data that allowed the team to connect birds’ known life histories with their individual song repertoires. But it’s likely that bird songs evolve over time in similar ways in other species and locations.
“We expect similar processes to occur in any species where learning plays a role,” says Recalde. “Having said that, how exactly population dynamics affect songs will depend on other factors, such as the timing of song-learning and the size of the song repertoire. Like human languages or music, bird song is rarely static.”
Words by Graeme Green – a British photographer and journalist with a passion for wildlife and conservation | Main image by David López Idiáquez (great tit in Wytham Woods)
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